Chlorpromazine equivalent

Class Agent (Brand Name) Dosage Range (mg/day) Chlorpromazine Equivalents (mg) Available Formulations... 

Chlorpromazine equivalents Approximate dose equivalent of a first-generation antipsychotic to 100 mg of chlorpromazine (relative potency). 

The overall mean chlorpromazine-equivalents per day (CPZe) dose prescribed differed significantly, with lower dosing in Thailand compared with Malaysia and Australia (p < 0.001) (see Table 11.4). Pairwise comparisons revealed that the mean typical antipsychotic dose was significantly higher in Malaysia compared with Thailand (p < 0.001) and NWMH (p < 0.001). There were significant differences observed (p < 0.001) while comparisons of the mean atypical antipsychotic dose showed that Australia was significantly higher compared with Thailand (p < 0.001) and Malaysia (p < 0.001). 

The dosages of antipsychotic drugs differed markedly between the six sites studied (see Table 12.2). Of note, there were more than 50% of patients in China, Hong Kong, Taiwan, and Singapore taking less than 600 mg chlorpromazine-equivalents... 

Of 23 patients with bipolar affective disorder taking neuroleptic drugs, 15 developed akathisia and 18 had parkinsonism during their entire inpatient treatment (217). The patients initially received high-potency neuroleptic drugs (maximum 2000 mg/day of chlorpromazine equivalents) and were assessed weekly. Akathisia developed in 44% of the patients with severe headache or nausea who received prochlorperazine 10 mg intravenously (n = 100) within 1 hour (218). None of the 40... 

In one study, previous neuroleptic drug use at study entry was the only significant predictor of tardive dyskinesia (296). Psychiatric outpatients aged over 45 years, who had taken neuroleptic drugs for 0-30 days (n = 176), were compared with 131 who had taken neuroleptic drugs for more than 30 days. The cumulative incidences of tardive dyskinesia were 23% and 37% at the end of 12 months. In the patients who had never used neuroleptic drugs before (n = 87), the mean cumulative incidence of tardive dyskinesia after the use of typical neuroleptic drugs (median dose 68 mg/day of chlorpromazine equivalents) was 3.4% at baseline and 5.9% at 1 and 3 months. 

Since the potency (therapeutic efficacy in relation to weight) of antipsychotic agents varies markedly between compounds, it is useful to think of the effective antipsychotic dose of classical agents in terms of chlorpromazine equivalents (see Table 19.5). For example, haloperidol has a relatively high anh-psychotic potency, such that 2-3 mg is equivalent to chlorpromazine 100 mg, whereas sulpiride 200 mg (low potency) is required for the same antipsychotic effect. 

For each antipsychotic agent there is a licensed maximum dose for example up to 1000 mg of chlorpromazine/day may be given under the United Kingdom licence. Prescribing beyond the licensed maximum dose requires specialist consent. When two antipsychotics are co-prescribed, the maximum antipsychotic dose should not exceed 1000 mg of chlorpromazine equivalents/day except under specialist supervision. For some antipsychotics the licenced maximum dose is considerably less than 1000 mg of chlorpromazine equivalents/day. For instance, the licenced maximum dose of thioridazine was reduced to 600 mg/day following concerns about its cardiovascular toxicity. Note... 

Key CPZ equiv dose = Chlorpromazine equivalent dose.This concept is of value in comparing the potency of classical antipsychotics. Dose ranges are not specified as they are extremely wide and drugs are normally titrated up from low starting doses (e.g. chlorpromazine 25 mg or equivalent) until an adequate antipsychotic effect is achieved or the maximum dose reached.The chlorpromazine equivalent dose concept is of less value for atypical antipsychotics since minimum effective doses (Min. eff. dose) and narrower therapeutic ranges have been defined. Maximum dose (Max. dose) can be exceeded only under specialist supervision. 

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